This circuit is from a 1990s publication by William Sheets. The circuit consists of a stage whose gain is adjusted according to the signal intensity.
This amplifier has a few Watt output, using old transistors. The speaker is 45 ohms, but with...
This circuit is from an old American documentation, from 1977, but it can be implemented with more...
This circuit was obtained from the CA3140 datasheet. This component consists of an operational amplifier...